CS254382B1 - A method for preparing a prefabricated contact lens - Google Patents

Abstract

A method of preparing a preform for turned contact lenses by polymerizing a solvent-free monomer mixture in the presence of a radical initiator, in which the obtained preform is allowed to swell in a swelling agent, low molecular weight fractions, monomer fractions or fractions of uncrosslinked homopolymer are washed out, and then the preform is thoroughly dried.

Description

BACKGROUND OF THE INVENTION The present invention relates to a process for preparing prefabricated parts for turned contact lenses from both conventional and multivalent materials.

The term prefabricated parts mean xerogel casting, both in the form of buttons and in the form of contact lenses made in the proposed molds by the oast molding method and the like.

To date, it is known to prepare lenses mainly in two ways. The centrifugal casting method produces lenses directly in the swollen state (U.S. Pat. Nos. 108,895,116,260) by polymerizing the monomer mixture in a rotating form in the presence of a solvent.

Most contact lens manufacturers use the classical method of machining xerogel precasts prepared by radical polymerization, respectively. copolymerization of vinyl hydrophilic monomers in the absence of a solvent. The precast prepared in this way can be further machined and polished only if the glass transition temperature Tg of the material is sufficiently high so that the surface to be machined is in the glass state for the entire machining time. This condition is not sufficiently fulfilled for multicellular copolymers whose more hydrophilic comonomers have a Tg lower than the temperature in the machined precast layer. For example, a crosslinked copolymer of monoethylene glycol monomethacrylate with dlethylene glycol monomethacrylate from 55 wt. The water after swelling is no longer mechanically workable into an optically matching contact lens.

The slow rate of polymerization in the high conversions of the polymerization system in the absence of solvent polymerization causes most of the precasts thus prepared to contain monomer and oligomer residues that wash out from the equilibrium swollen lens.

As a result, there is a loss of material from the finished product and hence changes in swollen contact lens parameters due to deformations in the base curves. These defects are particularly noticeable in polymer systems where two or more vinyl monomers having copolymers having unsuitable copolymerization parameters are copolymerized, so that up to 20% of the solubles can be determined in the final xerogel block by sol-gel analysis, which in some cases is clearly shown as homopolymers of individual poorly copolymerizing monomers. In this case, with each percent of monomeric and low molecular weight fractions in such a block, the glass transition temperature Tg is reduced by approximately 6 ° C, which makes or precludes the mechanical machining of the precast.

The disadvantages of the above-mentioned disadvantages are eliminated by a process for the production of a turned contact lens prefabricated polymerization of a solvent-free monomer mixture in the presence of a free-radical initiator. . The swelling agent may preferably be water, C 1 -C 7 aliphatic alcohols, dimethylsulfoxide, dimethylformamide alone or mixtures thereof, and the like. The washing is preferably carried out at a temperature of 40 to 200 ° C, depending on the swelling agent used, preferably a temperature close to the boiling point of the swelling agent. Washing can be carried out successively with different swelling agents. Thus, the prefabricated product is freed of soluble constituents in the swelling agent. Thereafter, the swollen hydrogel precast is heated above the Tg temperature of the respective copolymers in an atmosphere of superheated swelling agent vapor, optionally in the presence of air or inert gas, after which it is cooled and dried.

The drying can be advantageously carried out by transferring the prefabricated product to an oven where, in an atmosphere of superheated swelling agent vapor, above the temperature Tg of the respective copolymers, preferably in the range of 102 to 180 ° C, optionally in the presence of air or inert gas. it is cooled, eventually dried to constant weight, and transferred to a desiccator, where it is stored above the desiccant until processing into a contact lens. The advantage of drying the swollen prefabricates in superheated steam is that the removal of the polymerization solvent from the three-dimensional structure occurs under conditions of perfect mobility of the polymer chains and their side segments (i.e. above the glass transition temperature of the Tg gel). structure while maintaining the proportions of the external dimensions and angles of the dried prefabricate relative to the swollen, at a given initial composition, polymerization composition.

However, it is also possible to dry the swollen prefabricates freely in air under laboratory conditions, followed by drying to constant weight (dehumidification), preferably again in superheated steam. This method is economically undemanding but time consuming.

The precasts treated in this way are free of any undesirable solubles and ready for mechanical contact lens treatment. This means that with each percent of washed solubles (low molecular weight and uncrosslinked homopolymers) the Tg of xerogel increases by about 6 ° C, resulting in improved machining properties and polishing of the material. The method according to the invention ensures that the finished contact lens of the materials thus prepared will be free of any material loss after prolonged extraction with water or alcohol, and hence also without any changes in the optical parameters. The relationship between the parameters of the prefabricated xerogel replica and the prefabricated prefabricate is clear from the fact that by swelling the xerogel replica all dimensions are increased by the same factor.

In the following, the invention is illustrated by the following examples.

Example 1

2-hydroxyethlymethacrylate containing 0.4 wt. The ethylene glycol dimethyl acrylate was polymerized in the presence of 0.1 diisopropyl percarbonate at 60 ° C for 16 hours in a die casting mold. After this time the prefabricated product was transferred to a wash liquor (also possible in soxlet extractors) where it was washed with distilled water at 60 ° C until its swelling weight did not increase further (while checking the last extractions of the extractant UV spectroscopy). Then, the swollen prefabricated product was transferred to a 135 ° C oven containing a porous ceramic plate soaked with 50 ml of distilled water. This created an atmosphere enriched in the oven enriched with superheated steam. The precast was dried to constant weight. A contact lens having an optical power of -5.5 D, a diameter of 14.4 mm, a center radius of 8.70 and a center thickness of 0.20 mm in a swollen state was produced from such a perfectly dried xerogel precast.

Example 2

The precast prepared and washed with water according to Example 1 was placed in a thermostatic oven at 165 ° C, into which a stream was fed to the same temperature of superheated steam produced in the evaporator. This created an atmosphere of pure superheated steam. The result after complete drying of the precast was the same as in Example 1.

Example 3

The procedure was as in Example 1 except that the steam was generated by an excess of ethanol. The result was as successful as in the previous examples.

Example4

Polymerization mixture containing 85 wt. % N-vinylpyrrolidone and 15 wt. by anionic polymerization of the prepared fifty dimer methyl methacrylate with allyl methacrylate in a ratio of 15: 1 was polymerized in the presence of 0.2 wt. % diisopropyl percarbonate for 16 h at 60 ° C in the molds on the buttons. The obtained precast was transferred to a washing bath containing dimethylsulfoxide and swelled to constant weight. It was then condensed into water (again to constant weight) and dried according to Example 2. The obtained xerogel was successfully processed into a constant contact lens.

Example 5

Polymerization mixture containing 70 wt. % N-vinylpyrrolidone and 30 wt. % methyl methacrylate containing 1 wt. allyl methacrylate was polymerized in the presence of 0.5 wt. dlbenzoyl peroxide at 70 ° C for 16 h in the form of buttons. The obtained precast was transferred to a washing bath containing dimethylsulfoxide and swelled to constant weight. It was then condensed into water (again to constant weight) and dried according to Example 2. The obtained xerogel was successfully processed into a constant contact lens.

Example6

2-hydroxyethyl methacrylate with a content of 0.4 wt. ethylene glycol dimethacrylate was polymerized under radical polymerization conditions in the form of buttons. The obtained precast was transferred to a washing bath containing dimethylsulfoxide and swelled to constant weight. It was then condensed into water (again to constant weight) and dried according to Example 2. The obtained xerogel was successfully processed into a contact lens with constant parameters.

Example 7

Polymerization mixture of 2-hydroxyethyl methacrylate and ethyl methacrylate containing 0.4 wt. ethylene glycol dimethacrylate was polymerized under radical polymerization conditions, in the form of buttons. The obtained precast was transferred to a washing bath containing dimethylsulfoxide and swelled to constant weight. It was then condensed into water (again to constant weight) and dried according to Example 2. The obtained xerogel was successfully processed into a constant contact lens.

Example 1 a d 8 ,,

Polymerization mixture of 2-hydroxyethyl methacrylate and vinylpyrrolidone containing 0.4 wt. The ethylene glycol dimethacrylate was polymerized under radical polymerization conditions in the form of buttons. The obtained precast was transferred to a washing bath and further processed according to Example 1 with the same result.

Example9

The precast made from the vinylpyrrolidone graft copolymer to 2-hydroxyethyl methacrylate was transferred to a wash liquor and further processed according to Example 1 with the same result.

Example 10

The precast made from a copolymer of 2-hydroxyethyl methacrylate, methacrylic acid and vinylpyrrolidone was transferred to a wash liquor and further processed according to Example 1 with the same result.

Example 11

The precast made of methyl methacrylate-acrylic acid copolymer was transferred to a wash liquor containing dimethylsulfoxide and swelled to a constant weight. It was then condensed into water (again to constant weight) and dried according to Example 2. The obtained xerogel was successfully processed into a constant contact lens.

Example 12

The precast made of a copolymer of glyceryl methacrylate and methyl methacrylate was transferred to a washing bath containing dimethylsulfoxide and swelled to a constant weight. It was then condensed into water (again to constant weight) and dried according to Example 2. The obtained xerogel was successfully processed into a constant contact lens.

Example 13

The precast manufactured from a copolymer of glycidyl methacrylate and vinyl pyrrolidone was transferred to a washing bath containing dimethylsulfoxide and swelled to a constant weight. It was then condensed into water (again to constant weight) and dried according to Example 2. The obtained xerogel was successfully processed into a constant contact lens.

Example 14

The precast made from a copolymer of glycidyl methacrylate and 2-hydroxyethyl methacrylate was transferred to a wash liquor and further processed according to Example 1 with the same result.

Example 15

The precast made from a mixture of polyvinylpyrrolidone and poly-2-hydroxyethyl methacrylate was transferred to a wash liquor and further processed according to Example 1 with the same result.

Example 16

The precast made from a copolymer of 2-hydroxyethyl methacrylate, vinyl acetate and N, 1,1-dimethyl-3-oxobutyl acrylamide was transferred to a wash liquor containing dimethylformamide and swelled to a constant weight. It was then condensed into water (again to constant weight) and dried according to Example 2. The obtained xerogel was successfully processed into a constant contact lens. ^x

Example 17

The precast made of allyl-2-hydroxyethyl ether-diallylethe.ru copolymer was transferred to a wash liquor containing dimethylformamide and swelled to a constant weight. It was then condensed into water (again to constant weight) and dried according to Example 2. The obtained xerogel was successfully processed into a constant contact lens.

Claims (5)

SUBJECT OF THE INVENTION A process for the preparation of a turned contact lens polymerization by polymerizing a solvent-free mixture in the presence of a free-radical initiator, characterized in that the obtained precast product is swelled in a swelling agent, low molecular weight, monomeric or uncrosslinked homopolymer is washed. 2. A process according to claim 1 wherein the swelling agent is water, aliphatic alcohols containing 1 to 7 carbon atoms, dimethylsulfoxide, dimethylformamide alone, or mixtures thereof. 3. The method according to claim 1, wherein the washing is carried out at a temperature of 40 to 200 [deg.] C., depending on the swelling agent used. 4. A process according to claim 1, wherein the swollen hydrogel precast is heated above the glass transition temperature Tg of the respective copolymer in an atmosphere of superheated swelling agent, optionally in the presence of air or an inert gas, after which it is cooled and dried. Method according to Claims 1 to 4, characterized in that the washing is carried out successively by different swelling. reagents.